1. Field of Invention
The invention relates to a pressure-regulating airbag for ink cartridges and, in particular, to an airbag that is embedded in an ink cartridge and the assembly method therefor.
2. Related Art
The ink cartridge is an essential element for any inkjet pen. If there is no pressure-regulating device inside the cartridge, ink may leak out when the ambient pressure becomes low, for example, during transportation by air. This will result in unacceptable inkjet cartridge products. Moreover, unexpected temperature rise in the storage place is likely to increase the pressure inside the cartridge that may cause ink leakage too.
The importance of the pressure-regulating design of the ink cartridge is further seen in the continuous operation of an inkjet mechanism. As the ink is consumed, the ink volume becomes smaller, resulting in an increasing negative pressure. If the pressure is not appropriately tuned, the negative pressure may diminish or cancel with the ink ejection force from the inkjet chip, losing the ink droplet ejection precision. Eventually, the inkjet printer performance will be seriously affected. What is worse is that the internal negative pressure disallows the inkjet chip to eject ink before the ink is depleted.
There are already many patents or products with an ink cartridge negative pressure reduction mechanism. For example, a classic example is the U.S. Pat. No. 5,409,134. It proposed a design that used a thin plate spring to support the airbag. After then, various ideas were disclosed in accord with the pros and cons of the patent. However, most of the known designs put emphasis upon the variations and modifications in the pressure-regulating mechanisms, but the problem of how to increase the efficiency of assembling the inkjet cartridge and pressure-regulating element is never addressed.
An objective of the invention is to provide a negative pressure-regulating airbag that is embedded into an ink cartridge by pressing and the method for assembling it, so that the assembly of the airbag and the ink cartridge can be quickly and conveniently achieved.
In addition to a bag with a variable volume, the disclosed negative pressure-regulating airbag has a buckle ring, a plate, and an elastic element. The buckle ring is closely connected to the bag. A vent hole is formed in the middle of the buckle ring, allowing air to enter or escape the airbag when the ambient pressure changes. The buckle ring has a protruding part on the surface of the bag so as to be embedded into a preserved little hole on an ink cartridge by pressing during the assembly. This forms a quick and tight connection between the airbag and the ink cartridge. One end of the elastic element is connected to the ink cartridge and the other end to the plate so that the plate imposes a force to depress the airbag. This keeps the negative pressure inside the cartridge within a desired range to prevent ink leakage from the cartridge due to the ambient pressure change during transportation or use.